Knowing where to cut requires experience, intuition, and, frankly, a lot of trial and error.
However, Oscar-winning editor Walter Murch has a theory that might help the next time you're unsure of where to make an edit, that a human blink reads as "emotional punctuation" on-screen and could potentially serve well as transitions between shots. Editor Sven Pape puts Murch's theory to the test in this episode of This Guy Edits.
A lot can be learned from studying the eye movements in a scene. As Pape says in the video, a blink can be translated as the end of a character's thought or as a transition from one thought to another—which is basically what an edit is.
And now that you've seen this technique in action, it might be impossible to watch a film and not notice all the blinking going on. But keep in mind that this doesn't mean that a blink is always going to be the catalyst for an edit, but it does mean that they are kind of built-in edit points that can give you a good idea of where an edit could potentially be made.
Do you use Walter Murch's technique when you edit?